Device for changing an operational status of a shifting element with two shifting element halves

Abstract

A mechanism for changing the operating condition of a shifting element having two shifting element halves, which can either be functionally connected to connect two components or disengaged to break the connection between the components. The mechanism includes a drive machine and a drive converter unit in the area of which rotary drive motion of the drive machine can be converted into a translational actuation movement of the shifting element. A spring device is associated with the drive converter unit, whose spring force assists with actuating the shifting element in the engaging direction. The spring device includes an approximately circular flat spring element which, in at least one area of the drive converter unit, is in contact with at least one cam, whose stress condition varies as a function of an operating condition of the drive converter unit and is designed to be rotationally fixed.

Description

[0001]This application claims priority from German patent application serial no. 10 2011 006 965.8 filed Apr. 7, 2011.FIELD OF THE INVENTION[0002]The invention concerns a device for changing an operating condition of a shifting element with two shifting element halves.BACKGROUND OF THE INVENTION[0003]All-wheel vehicle drive-trains are increasingly made with frictional shifting elements by means of which, in each case, drive torque produced by an internal combustion engine, which is converted in the area of a transmission connected downstream from the internal combustion engine as a function of an overall gear ratio currently engaged in the transmission in an operating-condition-dependent manner, can be distributed in varying degrees between two driven vehicle axles of the all-wheel drive-train, in order to influence the driving behavior of the all-wheel vehicle, for example to increase the driving safety.[0004]To do this, the transmission capability of such shifting elements has to ...

AI Technical Summary

Benefits of technology

[0018]Accordingly, the purpose of the present invention is to provide a mechanism for changing the operating condition of a shifting element having two shifting element halves, which can be highly, efficiently operated with little control and regulation effort and which takes up little fitting space.

[0020]Compared with actuation systems known from the prior art and made with compensation devices, the mechanism according to the invention takes up less structural space since the spring device comprises an at least approximately circular flat spring element which, in a space-saving manner, co-operates with the drive converter unit without additional lever elements in the area of at least one cam with very small power loss and thus high efficiency, along with high control dynamics.

[0027]If a closing force to be applied to the shifting element in its closing direction is adapted as a function of a variation of an opening force that acts in the opening direction of the shifting element, produced during an actuation of the shifting element in the area of the shifting element, in such manner that an actuating force produced by the drive machine is preferably at least nearly constant at least within a predefined operating range of the shifting element, the maximum power of the drive machine required for actuating the shifting element can be limited with little effort and the mechanism according to the invention can be made in a space-saving manner.

[0030]If the shape of the cam has an assembly section in the area of which the flat spring element can be brought, during assembly, into functional connection with the cam in an operating condition that is essentially free from prestress, then in a simple manner the mechanism according to the invention can be assembled without force and, by then rotating the flat spring element relative to the drive converter unit, it can be brought into contact with another part of the cam's curve geometry and thereby changed to the prestressed condition required for later operation.

[0032]A further embodiment of the mechanism according to the invention that can be operated with good efficiency is made with a bearing device that is located in the area of the functional connection between the cam and the flat spring element, and by virtue of which frictional forces that occur during operation of the device between the cam and the flat spring element can be reduced simply and inexpensively.

[0035]If, as a function of the degree of closing of the shifting element, the flat spring element undergoes a varying elliptical deformation, especially an elliptical deformation whose extent increases as the closing degree increases, in a further embodiment of the mechanism the flat spring element is connected in a rotationally fixed manner to one of the devices in areas of lower radial deformation. This considerably reduces any friction force in the area of the rotationally fixed connection between the flat spring element and the device that is rotationally fixed thereto, and minimizes or completely avoids any undesired actuation hysteresis.

Problems solved by technology

In addition, for the design of the drive machine and the drive converter unit combined therewith, the wear of a shifting element that takes place over its operating life is also taken into account since enlargement of the air gap caused by wear increases the control path.

However, such a permanent current flow is undesirable since on the one hand it imposes a load on the electrical and electronic components, and on the other hand it increases the fuel consumption of the vehicle.

Disadvantageously, due to the low tooth efficiency in the area of a gear system designed to be self-locking, actuating systems with self-locking require a higher torque from the drive machine over the full operating range of a shifting element than do the actuating systems without self-locking.

However, higher actuating forces can only be provided with drive machines of corresponding power.

To produce a self-locking actuation system that occupies less fitting space, a transmission ratio between the drive machine and the shifting element can be correspondingly increased, but this compromises the control dynamics to a considerable extent.

However, the use of electromagnetic holding brakes entails additional control and regulation complexity and requires corresponding hardware for actuating the electromagnetic brakes, thus increasing the manufacturing and development costs.

In addition, when there are frequent demands for changing the operating condition of the frictional shifting element to be actuated, then due to the system-inherent control dynamics of the electromagnetic holding brakes, the holding effect that they provide cannot be used to the desired extent, so the current needed for operating the electric motor cannot be reduced as much as desired.

In each of the known compensation devices, a compensation spring is functionally connected by additional lever elements to a rotary plate, but this entails structural complexity and actuating systems made with such compensation devices also occupy an undesirably larger amount of fitting space.

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